textproduct: Albany

WHAT HAS CHANGED

Continued to increase PoPs and QPF for the Mid Hudson Valley this evening into tonight with a batch of showers and thunderstorms expected to track through. Increased PoPs to slight chance/chance for northern areas tomorrow afternoon as well for the possibility of isolated to scattered showers and thunderstorms. Finally, lowered temperatures Friday night especially for the ADKs and Catskills.

KEY MESSAGES

1) Some showers and thunderstorms are expected this evening into tonight especially south of I-90, with more isolated to scattered showers and storms possible tomorrow afternoon for northern areas.

2) Below normal temperatures expected this weekend into early next week. The weekend starts off dry, but shower and thunderstorm chances increase for Sunday into Monday.

DISCUSSION

KEY MESSAGE 1...As of 2:10 PM EDT...Current radar imagery shows some isolated to scattered showers that have developed over the last hour or so across the upper Hudson Valley. These showers are associated with an area of locally enhanced low-level convergence and relatively higher dew points per latest NYS mesonet obs. A weak upper shortwave tracking to the north is also adding some enhanced lift. Current SPC mesoanalysis shows a tongue of 500-1000 J/KG of MLCAPE extending down the Champlain/upper Hudson Valley area, so would not be surprised to see some thunder as well across northern areas through the next few hours. Low-level shear is unimpressive although deep-layer shear is more favorable for the upper Hudson Valley into southern VT. SPC has kept our area in just a general thunder risk this afternoon, but we can't totally rule out a few instances of gusty winds or even some hail for northern areas through the next few hours. That said, threat is isolated at best with lack of large-scale forcing and very low DCAPE values.

Better forcing arrives this evening into early tonight as another upper shortwave approaches from the west along with some increasing low-level theta e advection. Main focus will be for areas south of I- 90, for the southeastern Catskills and Mid Hudson Valley where an area/cluster of showers and storms is expected to track late this evening into tonight, departing into New England by late tonight. 12z HREF suggests SBCAPE values increasing to 500-1000 J/KG this evening for this area, while strengthening NW flow aloft will lead to increasing deep-layer shear up to 40-45 kt. Instability should start to wane after sunset as convection approaches from the west, which should prevent a widespread severe threat. SPC has a marginal risk for severe storms just to our west where the timing looks more favorable for severe weather. However, a few stronger storms can't be ruled out across the southeastern Catskills into the southern Mid Hudson Valley given the modest instability and increasing shear. Main hazard would be gusty winds, but with WBZ heights near or just below 10 kft and long straight hodographs, some marginally severe hail is also on the table this evening for these areas.

Will also mention increasing signal for some heavy downpours with this area of thunderstorms this evening into tonight. Storm motions should be fast with strengthening flow aloft, but some training appears possible with unidirectional flow parallel to a weak frontal boundary. CAMs have started to come around to this idea, with the 12z HREF suggesting a 50% chance for >1" of rain in 3 hrs for the Mid Hudson Valley tonight with some 1-1.5" rainfall totals showing up in the PMM. Fortunately, this looks more like a nuisance ponding of water type situation vs a flash flood threat with FFG values >1.75" in 1 hr for our southern counties.

While main batch of showers will track off to the east prior to sunrise tomorrow morning, some redevelopment of showers and storms is possible tomorrow afternoon with another upper shortwave and cold pool aloft tracking just north of the International Border. 12z HREF is suggesting up to 750-1000 J/KG of SBCAPE again for northern areas tomorrow overlapping with very strong deep-layer shear. However, questions remain about strength of the forcing and abundant mid-level dry air that may stifle convection. So, while threat is very conditional upon updrafts being able to get going tomorrow, a few stronger storms with gusty winds and/or marginally severe hail again are possible for the southeastern ADKs, upper Hudson Valley, and/or southern VT. SPC has kept us in a general thunder risk for now given the lackluster forcing and mid-level drying/subsidence. Will continue to evaluate guidance over the next 12-24 hrs and collaborate with SPC if an upgrade to a marginal risk may be warranted.

KEY MESSAGE 2...On Friday, a strong cold front will track across our region as a fairly strong upper shortwave dives southeastwards across NY. Despite the fairly strong forcing, capping aloft and lack of moisture should result in, at most, just a few isolated showers with the frontal passage. High pressure then builds into the region behind the front Friday night, remaining overhead into Sunday morning. Accordingly, have lowered temps from the NBM for western areas Friday night with favorable radiational cooling conditions expected. Low generally will be in the 50s for valley areas and low to mid 40s for the high terrain. Saturday looks like a gorgeous late-summer day with low humidity, mainly clear skies, and highs in the 70s. Latest guidance has trended slightly slower with the departure of the sfc high, so Saturday night will also likely feature lows in the 40s to 50s.

A fast-moving upper shortwave embedded in quasi-zonal flow aloft and associated sfc low tracking north of our area will bring the next chance for showers and possibly thunderstorms Sunday or Sunday night into Monday. Timing remains somewhat uncertain, so it remains to be seen how much of the day Sunday will remain rain free and whether or not timing of the frontal passage will align with daytime heating enough to allow for any stronger storms. Fortunately, temperatures are currently expected to remain slightly below normal through early next week.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

VFR conditions continue through 13/03z. Light westerly winds up to 10 knots continue this afternoon too. After 13/03z, there are low chances for KGFL, KALB, and KPSF on scattered rain showers through 7-9z. Confidence is higher for KPOU on timing for an isolated thunderstorm tonight between 3z and 5z, then scattered rain showers through 9z. However confidence is low on the potential impacts to terminals at this forecast period, so all shower or thunderstorm activity continues to be mentioned in PROB30 groups. Winds will become calm for the overnight period, with confidence for a period of low stratus clouds between 9z and 12z. Then VFR conditions gradually return between 11z and 13z through the end of the TAF period.

Outlook...

Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. Saturday Night: No Operational Impact. NO SIG WX. Sunday: Moderate Operational Impact. Chance of SHRA...TSRA. Sunday Night: Moderate Operational Impact. Likely SHRA...TSRA. Monday: Moderate Operational Impact. Chance of SHRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.